Diagnosing Newton’s Solver Convergence Failures in the Initialization of Modelica Models

Abstract

The convergence failure of iterative Newton solvers duringthe initialization of Modelica models is a seriousshow-stopper, particularly for inexperienced users. Thispaper presents the implementation in the OpenModelica toolof methods presented by two of the authors in a previouspaper, to help diagnosing and resolving these convergencefailure by providing ranked lists of potentially criticalstart attributes that might need to be fixed in order tosuccessfully achieve convergence. The method also provideslibrary developers with useful information about criticalnonlinear equations, that could be replaced by equivalent,less nonlinear ones, or approximated by homotopy for morerobust initialization.